The word entered English around 1470, from Latin. The pilgrim William Wey used it in his Itineraries, an account of his travels to the Holy Land, describing a wilderness where Christ fasted, and his body suffered, for forty days.
Latin probably carried the word first, in the ninth century, then French by the end of the twelfth, and Italian by the fourteenth, before it settled into English. By 1630, in Italian, the word had taken on its most enduring modern sense, tied to the Venetian custom of holding ships offshore.
Behind the Latin word lay a number, forty, built from quattuor, an older word meaning 'four'. Behind that lies a Proto-Indo-European root, *kwetwer-, meaning 'four'. The same root gave Greek tessares, its word for four.
FORTNIGHT and SQUARE share the same root. FORTNIGHT was formed within English, a contraction of an Old English phrase meaning 'fourteen nights', preserving an ancient Germanic custom of counting time by nights rather than days. SQUARE entered English in the mid-thirteenth century, from Old French, first naming a carpenter's tool used for measuring right angles.
For centuries the word marked periods of forty days in English law and religion. In the early sixteenth century it named the forty days a widow could remain in her late husband's house before her inheritance was settled, a right William Blackstone later described in his Commentaries on the Laws of England. Samuel Pepys, in 1663, noted that ships were being held for only thirty days, not forty, remarking that this went against the meaning of the word. By 1743 the same period of forty days also marked a set penance a servant might owe for wrongdoing.
